PCT International Published Patent Application No. WO 2006/009313 describes a control device for an internal combustion engine, which is used for injecting the fuel by a manifold injection and a direct injection, an injection ratio between the manifold injection and the direct injection being determined as a function of a speed of the internal combustion engine, a load factor, and of a temperature of a coolant of the internal combustion engine. In this context, a minimum injection quantity is always ensured for the direct injection in order to prevent the injection valve used for the direct injection from being clogged by deposits which accumulate on the direct injection valve at high temperatures. A cooling of the direct injection valve is effected by the minimum injection quantity.
The minimum injection quantity for the direct injection must be increased as a function of the temperature of the internal combustion engine in order to provide adequate cooling of the direct injection valve. Moreover, the homogeneity of the air-fuel mixture must be ensured regardless of whether the internal combustion engine is operated solely by direct injection, solely by manifold injection, or by a combination of direct injection and manifold injection. Certain operating states of the internal combustion engine require selecting a smallest possible minimum injection quantity for the direct injection. For example, a very small minimum injection quantity is selected for the direct injection in order to promote the homogeneity of the air-fuel mixture.